Answer:
I am stupid too, so forgive me if I am wrong.ಥ_ಥ
I am pretty sure the correct answer is D since 2 can be multiplied by 3 to get 6, and 3 can be multiplied by 3 to get 9. Thus, if the number of guitars is multiplied by 3, the number of amps will always be a multiple of 3.
